Geoffrey Woo, left, is one of Silicon Valley's biohackers — those who experiment with diet and medical devices in a DIY approach to biology. Melia Robinson/Business Insider

Geoffrey Woo likes to start the day with a plate of eggs, cheese, and avocado. It might not sound as if Woo — cofounder and CEO of "cognitive enhancement" supplements startup Nootrobox— is dieting.

But he subscribes to an increasingly popular diet — the ketosis or "keto" diet — that he hopes will help him live longer and better. It has especially gained traction among Silicon Valley's biohackers, who often experiment with diet and medical devices in a DIY approach to biology.

The high-fat, low-carb diet turns the body into a fat-burning machine. When you turn off access to glucose, a primary fuel source derived from eating carbohydrates, the body taps into its own fat stores for energy.

People find creative ways to fill up on these foods. In San Francisco, some dieters take their morning coffee with butter or a shot of coconut oil. The butter adds a silky, floral flavor.

So, what makes this "Atkins on steroids" diet so magical? It turns the body into a fat-burning machine.

A modern-day forager shows off his haul.
Melia Robinson/Business Insider

On a normal diet, the human body breaks down carbohydrates into glucose, which are used for energy or stored as glycogen in liver and muscle tissue. But the body has a plan B fuel supply.

When carbohydrates go missing from a person's diet — as happened when humans foraged for food — the body taps its fat stores for energy. The brain and other organs feed on ketones, a type of organic substance formed by the breakdown of fatty acids in the diet or body fat.

Eating healthy fats primes the body for this process, called ketosis.

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Studies on high-fat, low-carb diets suggest they can help dull hunger, promote weight loss, and improve markers of heart disease, though more research is needed.

Research out of Dr. Westman's clinic at Duke University supports a ketogenic diet as part of treatment for obesity, Type 2 diabetes, and fatty-liver disease, according to Time.

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A limited body of research suggest the keto diet may stave off diseases associated with aging, such as Alzheimer's and cancer.

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Mitochondria are known as the powerhouses of the cells. They take in nutrients and churn out energy for the cells. Research suggests a ketogenic diet may increase the number of mitochondria in brain cells, according to Scientific American.

When these "energy factories" are topped off, neurons in the brain may be better able to ward off stress from age-related brain diseases that ordinarily exhaust or kill the cells.

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Web searches for the diet have exploded since 2015, according to Google Trends. The keto diet has attracted a cult following of athletes, biohackers, and runway models.

Ferriss measures the level of ketones in his blood by pricking his finger and testing the blood with a device called the Precision Xtra from Abbott Laboratories, as many as four times a day.

In the Bay Area, an increasing number of techies follow another trendy diet, intermittent fasting, that has them going without food from 14 hours to several days. Many keep a keto diet on days when they're eating, or break their fast with a keto-friendly meal.